Clearing vehicle with tax exemptions (Kampala)

Hi Team,I am buying a vehicle from the bond. So far I have fully paid for the vehicle without duty. I have a back up note on this from USAID which the URA Commissioner approved for tax exemption. Everything is done now except the release documents from URA and allocation of number plates.URA advised that I should collect a letter from Ministry of Internal Affairs approving that I am tax exempt. Min of Internal Affairs says they do not deal with taxes and they cannot issue such letter. Lately I learnt that probably the letter should come from the Ministry of Finance. But again I am informed that the Ministry of Finance stopped handling tax issues and URA has been given full mandate to collect and refund taxes. Then I heard that the letter i need must come from the Ministry of External Affairs after USAID submit a formal request to them. Gentlemen/Ladies: does anyone know what I should do?